The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing systems are typically used to deposit and etch thin film on substrates such as semiconductor wafers. Examples of etching include wet chemical etching and dry etching. Dry etching may be performed using plasma generated by inductively-coupled plasma (ICP). The inductively-coupled plasma may be generated by coils arranged outside of a processing chamber adjacent to a dielectric window. Process gas flowing inside the processing chamber is ignited to create plasma.
Some ICP systems use two coils and flow current in the same direction in both coils. Etch rate maps tend to show an “M” shape etch pattern on the substrate surface where the maximum etch rate is at a mid-radius. The non-uniformity is generally not acceptable for some processes.